Example: math_ransac_plane3d_example

This example shows how to use MRPT’s RANSAC C++ template to detect planes from a 3D point cloud given as a matrix (each row is a point).

See also the RANSAC tutorial page.

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2023, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include <mrpt/gui/CDisplayWindow3D.h>
#include <mrpt/math/ransac.h>
#include <mrpt/opengl/CGridPlaneXY.h>
#include <mrpt/opengl/CPointCloud.h>
#include <mrpt/opengl/CTexturedPlane.h>
#include <mrpt/opengl/stock_objects.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/random.h>
#include <mrpt/system/CTicTac.h>

#include <iostream>

using namespace mrpt;
using namespace mrpt::gui;
using namespace mrpt::math;
using namespace mrpt::random;
using namespace mrpt::poses;
using namespace mrpt::system;
using namespace std;

void ransac3Dplane_fit(
    const CMatrixDouble& allData, const std::vector<size_t>& useIndices,
    vector<CMatrixDouble>& fitModels)
{
    ASSERT_(useIndices.size() == 3);

    TPoint3D p1(
        allData(0, useIndices[0]), allData(1, useIndices[0]),
        allData(2, useIndices[0]));
    TPoint3D p2(
        allData(0, useIndices[1]), allData(1, useIndices[1]),
        allData(2, useIndices[1]));
    TPoint3D p3(
        allData(0, useIndices[2]), allData(1, useIndices[2]),
        allData(2, useIndices[2]));

    try
    {
        TPlane plane(p1, p2, p3);
        fitModels.resize(1);
        CMatrixDouble& M = fitModels[0];

        M.setSize(1, 4);
        for (size_t i = 0; i < 4; i++)
            M(0, i) = plane.coefs[i];
    }
    catch (exception&)
    {
        fitModels.clear();
        return;
    }
}

void ransac3Dplane_distance(
    const CMatrixDouble& allData, const vector<CMatrixDouble>& testModels,
    const double distanceThreshold, unsigned int& out_bestModelIndex,
    std::vector<size_t>& out_inlierIndices)
{
    ASSERT_(testModels.size() == 1);
    out_bestModelIndex = 0;
    const CMatrixDouble& M = testModels[0];

    ASSERT_(M.rows() == 1 && M.cols() == 4);

    TPlane plane;
    plane.coefs[0] = M(0, 0);
    plane.coefs[1] = M(0, 1);
    plane.coefs[2] = M(0, 2);
    plane.coefs[3] = M(0, 3);

    const size_t N = allData.cols();
    out_inlierIndices.clear();
    out_inlierIndices.reserve(100);
    for (size_t i = 0; i < N; i++)
    {
        const double d = plane.distance(
            TPoint3D(allData(0, i), allData(1, i), allData(2, i)));
        if (d < distanceThreshold) out_inlierIndices.push_back(i);
    }
}

bool ransac3Dplane_degenerate(
    const CMatrixDouble& allData, const std::vector<size_t>& useIndices)
{
    return false;
}

// ------------------------------------------------------
//              TestRANSAC
// ------------------------------------------------------
void TestRANSAC()
{
    getRandomGenerator().randomize();

    // Generate random points:
    // ------------------------------------
    const size_t N_plane = 300;
    const size_t N_noise = 100;

    const double PLANE_EQ[4] = {1, -1, 1, -2};

    CMatrixDouble data(3, N_plane + N_noise);
    for (size_t i = 0; i < N_plane; i++)
    {
        const double xx = getRandomGenerator().drawUniform(-3, 3);
        const double yy = getRandomGenerator().drawUniform(-3, 3);
        const double zz =
            -(PLANE_EQ[3] + PLANE_EQ[0] * xx + PLANE_EQ[1] * yy) / PLANE_EQ[2];
        data(0, i) = xx;
        data(1, i) = yy;
        data(2, i) = zz;
    }

    for (size_t i = 0; i < N_noise; i++)
    {
        data(0, i + N_plane) = getRandomGenerator().drawUniform(-4, 4);
        data(1, i + N_plane) = getRandomGenerator().drawUniform(-4, 4);
        data(2, i + N_plane) = getRandomGenerator().drawUniform(-4, 4);
    }

    // Run RANSAC
    // ------------------------------------
    CMatrixDouble best_model;
    std::vector<size_t> best_inliers;
    const double DIST_THRESHOLD = 0.05;

    CTicTac tictac;
    const size_t TIMES = 100;

    math::RANSAC myransac;
    for (size_t iters = 0; iters < TIMES; iters++)
    {
        myransac.setVerbosityLevel(
            iters == 0 ? mrpt::system::LVL_DEBUG : mrpt::system::LVL_INFO);

        myransac.execute(
            data, ransac3Dplane_fit, ransac3Dplane_distance,
            ransac3Dplane_degenerate, DIST_THRESHOLD,
            3,  // Minimum set of points
            best_inliers, best_model);
    }

    cout << "Computation time: " << tictac.Tac() * 1000.0 / TIMES << " ms"
         << endl;

    ASSERT_(best_model.rows() == 1 && best_model.cols() == 4);

    cout << "RANSAC finished: Best model: " << best_model << endl;
    //  cout << "Best inliers: " << best_inliers << endl;

    TPlane plane(
        best_model(0, 0), best_model(0, 1), best_model(0, 2), best_model(0, 3));

    // Show GUI
    // --------------------------
    mrpt::gui::CDisplayWindow3D win("Set of points", 500, 500);
    opengl::Scene::Ptr scene = opengl::Scene::Create();

    scene->insert(opengl::CGridPlaneXY::Create(-20, 20, -20, 20, 0, 1));
    scene->insert(opengl::stock_objects::CornerXYZ());

    opengl::CPointCloud::Ptr points = opengl::CPointCloud::Create();
    points->setColor(0, 0, 1);
    points->setPointSize(3);
    points->enableColorFromZ();

    {
        std::vector<double> xs, ys, zs;

        data.extractRow(0, xs);
        data.extractRow(1, ys);
        data.extractRow(2, zs);
        points->setAllPoints(xs, ys, zs);
    }

    scene->insert(points);

    opengl::CTexturedPlane::Ptr glPlane =
        opengl::CTexturedPlane::Create(-4, 4, -4, 4);

    glPlane->setColor_u8(mrpt::img::TColor(0xff, 0x00, 0x00, 0x80));  // RGBA

    TPose3D glPlanePose;
    plane.getAsPose3D(glPlanePose);
    glPlane->setPose(glPlanePose);

    scene->insert(glPlane);

    win.get3DSceneAndLock() = scene;
    win.unlockAccess3DScene();
    win.forceRepaint();

    win.waitForKey();
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main()
{
    try
    {
        TestRANSAC();
        return 0;
    }
    catch (const std::exception& e)
    {
        std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << std::endl;
        return -1;
    }
}